Study on the Impact of Packing Methods on Thermal Performance of Packed-bed Thermal Storage Systems at Medium-low Temperature
By constructing physical and mathematical models of composite thermal storage in packed-bed systems,the impact mechanisms of multi-layer variable diameter filling and multi-layer cascade filling on the thermal storage characteristics of the packed-bed thermal storage system were studied at macroscopic scale based on the finite element method under medium and low temperature conditions.In the packed-bed thermal storage systems with multi-layer variable di-ameter and cascade filling,comprehensive analysis of indicators such as the liquid phase fraction of phase change capsules,temperature distribution,thermal storage rate,and thermal storage ef-ficiency were conducted to evaluate their thermal storage performance.The results showed that for conventional phase change capsule packed-bed systems with double-layer variable diameter is the economical and efficient structure under medium and low temperature,and the thermal stor-age rate of the d=30∶10 mm system increased by 27％compared to the single-layer system with d=30 mm.Converting conventional phase change capsules into phase change microcapsule can further improve the overall thermal storage performance of the system.The thermal storage rate is at least 1.73 times higher than that of the single-layer system with d=30 mm,and the ex-ergy efficiency is over 78％.However,the single-layer filling method is the optimal structure of the phase change microcapsule thermal storage system.The rock-phase change microcapsule cas-caded packed-bed thermal storage system combines the advantages of sensible and latent thermal storage,making it an optimized structure for packed-bed thermal storage systems under economic conditions.
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